JPS6081516A - Gas bearing device - Google Patents

Abstract

PURPOSE:To prevent the titled device from wearing, seizing and breaking by maintaining a gap between a rotary shaft and a housing at an initially determined value, by maintaining a temperature of the housing at the same level with that of the rotary shaft by providing a heat insulating device on the housing. CONSTITUTION:Heat of exhaust gas is transmitted to a shaft 23 from a turbine 21 on the one hand while it is transmitted to a center housing 26 and a journal bearing 29 from a turbine housing 24 and a thrust bearing 27, in a turbocharger. The shaft 23, consequently, the journal bearing 29 and the center housing 26 are heated up to about identical temperature. As the center housing 26, however, is covered with a heat insulating component 31, the center housing 26, the journal bearing 29 and the shaft 23 are kept at a predetermined temperature difference always. Then quantities of displacements of the shaft 23 and the bearing 29 become about indentical with each other, a gap 30 of which is kept at an initially determined value always.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in gas bearing devices, such as gas bearing devices used in automobile turbochargers, gas turbines, and the like.

(Prior Art) Conventional gas bearing devices, particularly air bearing devices used in turbomachinery, include the one shown in Figure 1 ("Lubrication" No. 15 @ No. 9, p. 595-p. 601,
Written by Fufu Jugo ``Current status of practical application of gas bearings in Japan'' 1
Published in 1970, see). This is an example in which a static pressure air bearing device is applied to an expansion turbine.
indicates the compressor impeller and these turbines 1
and the impeller 2 are integrally coupled by a shaft 3 which is a common rotation axis. Further, 4 is a turbine housing, 5 is a compressor housing, and both housings 4.5 are a center housing 6 into which the shaft 3 is loosely inserted.
are connected by. Inside the center housing 6, a journal bearing 7 that forms a small gap with the shaft 3 and a thrust bearing 8 arranged at the end of the shaft 3 of the two impellers are fitted and fixed. A compressed air supply hole 11.12 with a throttle valve 9.10 is formed in each of these two bearings 7.8. Also, 13
is the air supply pipe connected to these air supply holes 11.12,
Compressed air is supplied from a supply source (not shown) through an air supply pipe 13 and an air supply hole 1.
1 and 12, the gap G between the shaft 3 or impeller 2 and the bearing 7.8 is supplied. Zunawaji, this air bearing device supplies compressed air (pressurized air) to the bearing surface of the rotating body, so that the rotating body (particularly the shaft 3) can be removed from the bearing part.
The rotating body is floated and rotatably supported under extremely small frictional resistance compared to the viscous resistance caused by lubricating oil.

However, in such a conventional air bearing device, heat from the turbine 7 exposed to high temperature (e.g. 800°C) exhaust gas is transferred to the shaft 3 and the shaft 3 becomes high temperature, whereas the shaft 3 becomes high temperature. The center housing 6 and the journal bearing 7 fixed to the housing 6 are exposed to heat from the outside air and become lower in temperature compared to the shaft 3. As a result, due to the difference in thermal expansion with the shirt I-3, the shaft 3 The gap between the shaft 3 and the bearing 7 is pinched, and the shaft 3 and the bearing 7 come into sliding contact due to vibrations during high-speed rotation, causing IW wear, burning, and even damage.

(Object of the Invention) Therefore, the present invention maintains a housing that forms a predetermined gap with a rotating shaft at a temperature equivalent to that of the rotating shaft, so that the gap is always maintained at an initial setting value. The purpose is to eliminate the risk of wear, damage, and damage.

(Configured in the Invention) In the gas bearing device according to the present invention, the rotating shaft of the impeller that is rotationally driven by working gas is inserted into the housing with a predetermined gap, and the gap is filled with compressed gas to rotate the impeller. In a device that rotatably supports a shaft, the housing is configured to be maintained at a predetermined temperature by a heat retaining means.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows an embodiment of the present invention, which is a hydrostatic air bearing device applied to a turbocharger. That is, engine exhaust gas is used as the working gas, and compressed air is used as the compressed gas. First, to explain the configuration, in FIG. 2, numeral 21 is an exhaust turbine (impeller) rotationally driven by exhaust gas (working gas) of the engine, and numeral 22 is a wheel of the intake compressor, that is, an impeller. These turbine 21 and impeller 22 are coupled by a common rotation axis, that is, a shaft 23. Further, the turbine 21 is placed in the turbine housing 24, the impeller 22 is placed in the compressor housing 25,
The shirts 1 to 23 are rotatably housed with a slight gap between them, and the shirts 1 to 23 are loosely inserted into a center housing 26 that connects both housings 24 and 25. Specifically, both ends of the center housing 2G are connected to both housings 24.25 by disc-shaped thrust bearings 27.2) 3.
A substantially cylindrical journal bearing 29 is fitted between the center housing 26 (inside the center housing 26).

Fixed. Further, a predetermined gap 3o (for example, 10 μ) is formed between the journal bearing 29 and thrust bearings 27, 28 and the shaft 23. Furthermore, a cylindrical heat insulating member 31 is fitted to the outer circumferential portion of the center housing 26, and the heat insulating member 31 prevents the center housing 26 from being directly exposed to the outside air and allows the housing 26 to be connected to the shaft 23. It constitutes a heat retention means that maintains the temperature at approximately the same level as the temperature. Further, the journal bearing 29 has an orifice 32. A plurality of air supply holes 32 are formed, and the gap 30 between the bearing 29 and the shaft 23 is
Compressed air at a predetermined pressure is supplied through the air supply hole 32 from an air supply pipe 33 connected to a compressed air source (not shown). Further, this air supply pipe 33 is connected to each of the above-mentioned thrust bearings 27.2.
The compressed air also communicates with the air supply holes 34.35 formed at 8, and the compressed air passes through these air supply holes 34.35 and reaches a predetermined pressure in the gaps between each thrust bearing 27.28, the cylinder 2I, and the impeller 22. Supplied by

Note that air holes 32A, 34A, and 35A are formed in these air supply holes 32, 34, and 35, respectively. 36 is a bearing compressed air exhaust pipe connected to the gap 30.

Next, the effect will be explained.

The turbocharger uses high temperature (approximately 800°C) from the engine.
When the turbine 21 is rotationally driven by the exhaust gas (working gas), the impeller 22 connected to the turbine 21 by a shaft 23 also rotates together to compress the intake outside air and supply it to the engine. In this case, compressed air at a predetermined pressure is supplied from the air supply pipe 33 to the gap 30 on the outer peripheral surface of the shaft 23 and the gaps between the turbine 21 and the impeller 22 through the air supply holes 32, 34, and 35. As a result, the rotating body consisting of the turbine two impeller 22 and the shaft 23 floats above each bearing surface and rotates at high speed with extremely low friction. Also,
Each of the above-mentioned gaps (30, etc.) is formed as small as, for example, about 10 μm in order to increase the load capacity of the bearing.

At this time, the heat of the exhaust gas is transferred from the turbine 21 to the shaft 23 on the one hand, and from the turbine housing 24 and the thrust bearing 27 to the center housing 26 and the journal bearing 29 on the other hand. As a result, the shaft 23, journal bearing 29, and center housing 26 are heated to approximately the same temperature (for example, 400° C.). However, in this embodiment, the center housing 26 is
Since the housing 26 is covered by the heat member 31 and is not directly exposed to the outside air, the temperature of the housing 26 is lower than that of the shaft 23.
It will not be much lower than that of . That is, the center housing 26, journal bearing 29, and shaft 23 always maintain a constant temperature difference. As a result, the amount of thermal displacement between the shaft 23 and the bearing 29 is approximately the same, and the gap 30 between them is always maintained at the initial setting value of 10μ.

Next, FIG. 3 shows another embodiment of the present invention. In this embodiment, an air layer 41 is formed around the center housing 26 instead of the heat insulating member 31 in the above embodiment, and this air layer 41 is used as a heat retaining means. In other words, the thermal conductivity of air is lower than that of the metal forming the housing 2G compared to fluorine, and it has a heat retaining effect. This air layer 41 is formed between the pipe 42 and the housing 26 by fitting a cylindrical member (pipe) 42 onto the outer peripheral surface of the center housing 26 . The other configurations and operations are the same as those of the above embodiment, and will therefore be omitted.

Further, FIG. 4 shows still another embodiment of the present invention. The heat retaining means in this embodiment is the center housing 2
This configuration introduces engine exhaust gas into the outer periphery of G, and this high-temperature exhaust gas causes the center housing 26 to move toward the turbine 21.
The shaft 23 and the journal bearing 29 are kept at the same temperature, and the gap 3o between them is kept at a constant value. That is, a space 5I is formed on the outer periphery of the center housing 26 by a pipe 50, and this space 51 is connected to the turbine 21 by an inlet pipe 52.
It communicates with 3. In addition, this space 5 is provided by the exhaust pipe 54.
1 also communicates with the downstream exhaust path of the turbine 21. The other configurations and operations are the same as those in each of the embodiments described above, and will therefore be omitted.

(Effects) As explained above, according to the present invention, the gap filled with compressed gas between the rotating shaft and the housing can be maintained at the initial IM setting value, and the gap between the rotating shaft and the bearing can be maintained at the initial IM setting value. It is possible to completely prevent wear, seizure, and even damage to the bearing device itself due to solid contact.

Further, according to each of the above embodiments, the durability of the device itself can be improved by extremely simple modification of the bearing device (with a slight increase in cost and work).

[Brief explanation of drawings]

Figure 1 shows a cross section of a conventional gas bearing device.
The figure is a cross-sectional view showing one embodiment of the gas 11id+ receiving device according to the present invention, FIG. 3 is a cross-sectional view showing another embodiment of the present invention, and FIG. 4 is a cross-sectional view showing still another embodiment. It is a diagram. 21-----Turbine (impeller), 23-Shaft (rotating shaft), 26----~--Center housing, 30-----One gap, 31.41.5] ---Heat insulation means. Patent Applicant Nissan Motor Co., Ltd. Representative Patent Attorney Agagun Part

Claims (1)

[Claims] A gas bearing structure in which a rotating shaft of an impeller rotationally driven by working gas is inserted into a housing with a predetermined gap therebetween, and this gap is filled with compressed gas to rotatably support the rotating shaft. A gas bearing device characterized by being provided with a heat retaining means for maintaining a housing at a predetermined temperature.